Oxidation reactions are characterized by the gain or loss of what particle?

Oxidation reactions are defined by the loss of electrons. When a substance undergoes oxidation, it experiences an increase in oxidation state due to the removal of electrons, while another substance typically gains those electrons, undergoing reduction. This electron transfer is crucial in various biological processes, including cellular respiration and photosynthesis, where energy transformation occurs through redox reactions.

The focus on electrons makes option C the correct choice, as protons and neutrons do not participate in these energy transformation reactions in a manner characteristic of oxidation. While protons can influence the charge of a molecule, it is the transfer of electrons that directly defines the oxidation process. Nucleons, which comprise protons and neutrons in atomic nuclei, are not involved in redox reactions at all. Understanding oxidation and reduction in terms of electron transfer is essential for grasping many biochemical mechanisms.